Similarly increased serum IgA1 and IgA2 subclass antibody levels against Klebsiella pneumoniae bacteria in ankylosing spondylitis patients with/without extra-articular features.

IgA1 and IgA2 subclass serum antibodies against whole Klebsiella pneumoniae bacteria were studied earlier in the sera of 98 patients with ankylosing spondylitis (AS) and in 100 healthy blood donors by enzyme immunoassay. In this study, the patients were divided into groups according to the clinical picture, i.e., the presence or absence of iritis and enthesitis. The previous findings of increased IgA1 and IgA2 subclass antibody levels against K. pneumoniae in AS patients when compared to the healthy controls were not specifically associated with any single AS patient group in the present study, but instead were similarly seen in all patient groups with/without extra-articular features. This is in line with the previous studies suggesting a role for K. pneumoniae in the pathogenesis of AS.